全文获取类型
收费全文 | 202篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
化学 | 123篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 48篇 |
物理学 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 13篇 |
2012年 | 20篇 |
2011年 | 11篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 4篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有217条查询结果,搜索用时 15 毫秒
11.
The formation of inclusion complexes of six essential oil (EO) components (β-caryophyllene, cis-ocimene, trans-ocimene, sabinene hydrate (thujanol), γ-terpinene and α-terpineol) with six cyclodextrins (CDs) (α-CD, β-CD, γ-CD, HP-β-CD, RAMEB and CRYSMEB) was investigated by using static headspace-gas chromatography and UV–visible spectroscopy. Retention studies showed that CDs could efficiently reduce the volatility of EO components except for β-caryophyllene with α-CD. In this case, no inclusion complex was detected while for other compounds the formation of 1:1 inclusion complexes was observed. Results revealed that the inclusion stability mainly depends on geometric complementarity between encapsulated molecule and CD's cavity. Molecular modelling was used to investigate the complementarities between host and guest. Thus, CDs could efficiently be regarded as promising encapsulants for EO components leading to improve their application in cosmetic, pharmaceutical and agriculture fields. 相似文献
12.
Gayatri Mohanto S. R. Abhilash D. Kabiraj N. Madhavan R. K. Bhowmik 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1129-1131
Targets of isotopically enriched 170Er (erbium) were prepared on 45 μg/cm2 carbon backing using the method of vacuum evaporation. Another layer of carbon with thickness 23 μg/cm2 was deposited on it as a protective cap with the help of an electron gun. Carbon backing, Er and the capping carbon layer were deposited using resistive heating and electron gun deposition without disturbing the vacuum. The thickness of 170Er was measured by X-ray fluorescence analysis as well as with Rutherford backscattering spectrometry and it was found to be 150 μg/cm2. Successful preparation of sandwiched targets was very sensitive to substrate temperature, deposition rate, duration of in situ annealing, cooling rate etc. 相似文献
13.
Aliona Ghendov-Mosanu Daniela Cojocari Greta Balan Antoanela Patras Ildiko Lung Maria-Loredana Soran Ocsana Opri Elena Cristea Rodica Sturza 《Molecules (Basel, Switzerland)》2022,27(5)
The article focuses on the optimization of the extraction process of biologically active compounds (BAC) from grape marc—a by-product of the wine industry. The influence of temperature, specifically 30 °C, 45 °C and 65 °C, and ethanol concentration in solutions, specifically 0–96% (v/v) on the extraction yield of polyphenols, flavonoids, tannins and anthocyanins, were investigated. The composition of individual polyphenols, anthocyanins and organic acids, antioxidant activity (DPPH and ABTS) and CIELab chromatic characteristics of the grape marc extracts (GME), were characterized. The microbiostatic and microbicidal effects in direct contact of GME with pathogenic microorganisms, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, were determined in vitro. The influence of extraction parameters on the total polyphenol content (TPC), total flavonoid content (TFC), tannin content (TC), total anthocyanin content (TAC) and their interdependencies were studied using information analysis. A mathematical model was developed on cubic spline functions. The analysis of individual compounds showed the presence of a wide range of flavonoids (procyanidin B2, procyanidin B1, hyperoside and quercetin), flavones (catechin), hydroxybenzoic acid derivatives (gallic, protocatechuic, p-hydroxybenzoic acids, m-hydroxybenzoic acid, syringic acid), hydroxycinic acid derivatives and ferulic acid methyl ester. The malvidol-3-glucoside was the main anthocyanin identified in the extract. A high amount of tartaric acid was also found. GME showed significant antimicrobial activity against Gram-positive bacteria and lower activity against Gram-negative bacteria. 相似文献
14.
Mirela-Fernanda Zaltariov Angelica VladMaria Cazacu Sergiu ShovaMihaela Balan Carmen Racles 《Tetrahedron》2014
The new dicarboxylic acid, 1,3-bis(p-carboxyphenylene-ester-methylene)tetramethyldisiloxane (H2L, 1) was obtained by treating 1,3-bis(chloromethyl)-1,1,3,3-tetramethyldisiloxane with a mixture of terephthalic acid and terephthalic acid sodium salt in a 1:1 ratio. In this approach, besides the desired compound 1 (33 wt % yield), the condensation cyclic dimer 2 (7 wt % yield) and an oligomer 3 (10 wt % yield) resulted. The reaction between dicarboxylic acid H2L, where L is the carboxylate ligand, along with imidazole as co-ligand, and copper hydroxide resulted in the formation of a coordination compound [Cu(HIm)4(H2O)2]L·4.5H2O (4). Single-crystal X-ray crystallography has revealed that the crystal structure of 4 is a self-assembled H-bonded three-dimensional supramolecular structure. FTIR and NMR spectral techniques were also used to characterize the formed structures. Optical and thermal properties of all compounds were studied. The stability of the supramolecular structure in solution (methanol) and with temperature was studied using ATR-FTIR. The ability of the macrocycle 2 to bind potassium cations in solution was investigated by UV–vis spectrophotometry. 相似文献
15.
Electrochemical Behaviour and Rapid Determination of L‐Dopa at Electrochemically Pretreated Screen Printed Carbon Electrode
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Andreea Alexandra Rabinca Mihaela Buleandra Adriana Balan Ioan Stamatin Anton Alexandru Ciucu 《Electroanalysis》2015,27(10):2275-2279
A simple and rapid voltammetric method based on a disposable electrochemically pretreated screen‐printed carbon electrode is proposed for the determination of L ‐dopa. Under optimum differential pulse voltammetry conditions a limit of detection of 3.6×10?7 M for L ‐dopa was obtained. The method was successfully applied to the determination of L ‐dopa in a commercial pharmaceutical formulation. 相似文献
16.
The direct formation of alpha-methylene-beta-amino acid derivatives is achieved using the aza version of the Baylis-Hillman protocol. The products are readily formed in a three-component one-pot reaction between arylaldehydes, sulfonamides, and alpha,beta-unsaturated carbonyl compounds. The reaction is efficiently catalyzed by titanium isopropoxide and 2-hydroxyquinuclidine in the presence of molecular sieves. The protocol allows for structural variation of the substrates, tolerating electron-poor and electron-rich arylaldehydes and various Michael acceptors. 相似文献
17.
18.
Michaël Balan 《Transformation Groups》2013,18(2):329-359
We consider a desingularization Γ of a Richardson variety in the variety of complete flags, obtained as a fibre of a projection from a certain Bott-Samelson variety Z. For any projective embedding of Z via a complete linear system, we construct a basis of the homogeneous coordinate ring of Γ inside Z, indexed by combinatorial objects which we call w 0 -standard tableaux. 相似文献
19.
Merve Sendur Abidin Balan Derya Baran Levent Toppare 《Journal of polymer science. Part A, Polymer chemistry》2011,49(18):4065-4070
Tuning the bandgap of electrochromic polymers is one of the important research topics in electrochromism. To understand clearly the effect of donor unit in donor–acceptor–donor‐type polymers, 2,3‐bis(4‐tert‐butylphenyl)‐5,8‐di(thiophen‐2‐yl)quinoxaline and 2,3‐bis(4‐tert‐butylphenyl)‐5‐(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐ 5‐yl)‐8‐(thiophen‐2‐yl)quinoxaline were synthesized and polymerized potentiodynamically. Their electrochemical and spectroelectrochemical studies were performed, and the results were compared with those of poly(2,3‐bis(4‐tert‐butylphenyl)‐5,8‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)quinoxaline) (Gunbas et al., Adv Mater 2008, 20, 691–695). A blue shift in the polymer π–π* transitions revealed that the bandgap of such polymers with the same acceptor unit is related to the electron density of donor units. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
20.
Umut Bulut Abidin Balan Cagin Caliskan 《Journal of polymer science. Part A, Polymer chemistry》2011,49(3):729-733
Two benzotriazole derivative dyes 4,7‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)‐2‐dodecyl‐2H‐benzo[1,2,3]triazole, and 2‐dodecyl‐4,7‐bis(4‐hexylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole are shown to work as efficient photosensitizers for a diphenyliodonium salt initiator in cationic photopolymerization of epoxide and vinyl monomers. Substituted thienyl groups are attached to benzotriazole backbone to extend conjugation and enhance electron density of the molecules. Thereby, it was possible to initiate polymerizations at room temperature using long wavelength UV and visible light. The progress of photopolymerizations was monitored using optical pyrometry. The photopolymerization of an epoxide monomer using solar irradiation was also demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献